NIST (National Institute of Standards and Technology) using Vic-3D for digital image correlation (DIC)

NIST is using the Vic-3D digi­tal image cor­re­la­ti­on (DIC) sys­tem to ana­ly­ze stress in brid­ges. By using DIC, they try to under­stand the impact of stres­ses and strains on the metal con­nec­tors of brid­ges in order to avoid dama­ge or failure.


NIST is pre-strai­ning a wide pla­te with digi­tal image cor­re­la­ti­on (DIC) to deter­mi­ne the small-sca­le spe­ci­men sec­tio­n­ing plan:

https://www.nist.gov/video/pre-straining-pipeline-steel-plate


NIST is con­duc­ting a CWP test with digi­tal image cor­re­la­ti­on (DIC) to deter­mi­ne local and remo­te strains used to deter­mi­ne the Ten­si­le Strain Capa­ci­ty of a fla­wed pipe girth-weld:

https://www.nist.gov/video/curved-wide-plate-testing


NIST is making an SE(T) test with digi­tal image cor­re­la­ti­on (DIC) showing the asym­metric strain gra­di­ent of a spe­ci­men not­ched in the heat-affec­ted zone:

https://www.nist.gov/video/single-edge-notch-tension-testing

DIC measurements on structural concrete

The ETH Zürich — one of our long­stan­ding cus­to­mers — pro­vi­des on the fol­lowing web­site their rese­arch pro­ject. They ana­ly­ze the accu­ra­cy of digi­tal image cor­re­la­ti­on wit­hin the scope of rein­for­ced con­cre­te. Prof. Dr. Wal­ter Kauf­mann and Dr. Jai­me Mata Fal­cón are mem­bers of the project.

   eth-zuerich-2

Full-field strain mea­su­re­ment in rebar tension 

test: fail­u­re pha­se.

Strain Gauge Comparison

In this examp­le a Vic-3D mea­su­re­ment with 5MP CMOS Came­ra was per­for­med. The acryl spe­ci­men is fixed in a ten­si­le tes­ting machi­ne. A strain gau­ge is atta­ched at the back in com­bi­na­ti­on with a SCAD 500 strain gau­ge ampli­fier. The out­put of the SCAD 500 was con­nec­ted to the DAQ of the DIC sys­tem. The strain results are recor­ded par­al­lel with the Vic-3D mea­su­re­ment and plot­ted in a dia­gram. The came­ra type is equip­ped with Sony 5Mpx Pre­gius sen­sor, 75 fps.

Strain Gauge Comparison-1  Strain Gauge Comparison-1a

Image 1: Vic-3D mea­su­re­ment of the acryl specimen

 

Strain Gauge Comparison-2

 

 

 

 

 

 

 

 

Image 2: Com­pa­ri­son of strain gau­ge data (red cur­ve) and DIC Strain data (black curve)

 

The Vic-3D data match near­ly per­fect with the strain gau­ge data. Even at low strains the dif­fe­rence is less than 25 micro strain.

NDT of Carbon-NOMEX (honeycomb core) composite: Dynamic loading on a large yacht hull

Mari­ne NDE (Spain) used the tech­ni­cal advan­ta­ges of our She­aro­gra­phy-Sys­tem espe­cial­ly in com­bi­na­ti­on with the dyna­mic exci­ta­ti­on for non-dest­ruc­ti­ve exami­na­ti­on (NDE) of lar­ge are­as such as com­ple­te yacht hul­ls (see image below). The hull with a lenghts of 30,5m was a car­bon-fir­ber-com­po­si­te and part of high per­for­mance sai­ling yacht in build. Becau­se of the full-field method (100% of the inspec­ted area is exami­ned), the tes­ting of the ent­i­re hull requi­red only 240 shots, in three workdays.

 

The yacht hull con­sists of a sand­wich con­struc­tion, whe­re are in par­ti­cu­lar used honey­comb cores (NOMEX).

Marine NDT1Marine NDT2

 

 

 

 

 

 

On the left — A she­aro­gram of a detec­ted bon­d­ing defect (in red oval). The yel­low X marks the loca­ti­on of the core sam­ple shown at the right. The dest­ruc­ti­ve test con­firms the shearogram’s indi­ca­ti­on that the­re is a signi­fi­cant never-bond bet­ween the honey­comb core mate­ri­al and the film adhe­si­ve in this area.

 

Deformation Measurement

The fol­lowing video clips show a defor­ma­ti­on- or strain-mea­su­re­ment of a metal spring ele­ment, mea­su­red by using Vic-3D.

The first defor­ma­ti­on mea­su­re­ment would be made in the X direction.

 

The second defor­ma­ti­on mea­su­re­ment would be made in the Y direction.

 

The third defor­ma­ti­on mea­su­re­ment would be made in the Z direction.

 

In the last case you see the result of the strain measurement.

Motion Measurement on Rear Swinging Fork

The video shows the app­li­ca­ti­on of a ste­reo image cor­re­la­ti­on (pha­se syn­chro­ni­zed) for a three-dimen­sio­nal dis­pla­ce­ment mea­su­re­ment or move­ment ana­ly­sis (Vic-3D).

The used ste­reo came­ra sys­tem is based on two 5 Mpi­xel came­ras with a frame rate of 6Hz (at full reso­lu­ti­on) in com­bi­na­ti­on with the isi-sys syn­chro­niz­a­ti­on and trig­ger device for stro­bo­scopic obser­va­ti­on of perio­dic events.

X

Four mea­su­re­ment are­as (hydrau­lic cylin­der — below, wheel hub — left, swing­arm — midd­le and line­ar unit — right abo­ve) with speck­le pat­terns were moni­to­red for the eva­lua­ti­on. The vec­tor arrows repre­sent the cur­rent dis­pla­ce­ment state.

 

Combination Stereomicroscope and Vic-3D digital image correlation

App­li­ca­ti­on examp­les of a spe­cial ste­reo­mic­ro­scope in com­bi­na­ti­on with Vic-3D digi­tal image cor­re­la­ti­on on elec­tro­nic components.

Stereomikroskop

Image 1: Mea­su­re­ment setup

Mea­su­re­ment set up: Ste­reo micro­scope moun­ted on x‑y-z-micro­ta­ble (backside) and ten­si­le machi­ne (right).

Stereomikroskop2

Image 2: Strain in x‑direction

Stereomikroskop3

Image 3: Strain in y‑direction

Strain dis­tri­bu­ti­on of a half cut capa­ci­tor-chip (left part) and its sol­de­ring area (round sec­tion). The board is under
ben­ding load. The board is ver­ti­cal on the right sight of the image. The local red area is showing a crack in the
sol­de­ring part. Image area approx. <2mm.

 

Lötkugel

Image 4: The main strain of mea­su­ring a sol­der ball d=300µm under hori­zon­tal she­ar stress is shown.